Package steam generator

ABSTRACT

A package steam generator is disclosed which comprises longitudinally extending upper and lower drums having their center lines laterally displaced from one another. First and second sections of tubing extend between the drums to define therebetween a furnace area for heating the fluid in the tubing. The tubes are of substantially equal length in both tubing sections to provide substantially uniform fluid circulation between the drums, thereby to prevent unequal heating and failure of the tubing.

United States Patent Seelinger [54] PACKAGE STEAM GENERATOR [72] Inventor: Richard W. Seelinger, East Stroudsburh,

[73] Assignee: Ovitron Corp., Newburgh, NY.

[22] Filed: Mar. 13, 1970 211 Appl. No.: 19,168

[52] U.S. Cl ..122/336 [51] Int. Cl ..F22b 21/34 [58] Field ofSeai-ch ..l22/235,332,333,336, 347

[56] References Cited UNITED STATES PATENTS 2,630,790 3/1953 Miller ..l22/347 3,518,973 7/1970 Herzenberg ..122/235 [451 May 23,1972

FOREIGN PATENTS OR APPLICATIONS 879,115 10/1961 Great Britain ..l22/336 Primary ExaminerKenneth W. Sprague Att0rneySandoe, Hopgood & Calimafde [57] ABSTRACT A package steam generator is disclosed which comprises longitudinally extending upper and lower drums having their center lines laterally displaced from one another. First and second sections of tubing extend between the drums to define therebetween a furnace area for heating the fluid in the tubing. The tubes are of substantially equal length in both tubing sections to provide substantially uniform fluid circulation between the drums, thereby to prevent unequal heating and failure of the tubing.

3 Claims, 7 Drawing Figures PATENTED MAY 2 3 I972 3 6 6 4. 3 O 9 INVENTOR film/172D W. SEEM/V 5? ATTOR Y5 PATENTEDMAY23 I972 3.664, 309

sum 3 [IF 3 FIG. 7

INVENTOR mango w. SEILIN G-ER g I v iTTORNEYfi Z PACKAGE STEAM GENERATOR The present invention relates generally to steam generating units, and particularly to a water-tube packaged steam generatOl.

Because of its many advantages, the use of packaged steam generators or boilers has increased over the years to a point where it constitutes a significant portion of all the steam generators presently being manufactured and sold. The packaged generator rather than being assembled at the point of eventual use, is fabricated as a single unit in a boiler shop at which the basic elements of the generator, such as the water drums, tubing, furnace, and walls, are assembled. This has the advantage of significantly reducing the construction cost of the boiler by permitting all the work to be done at a single location, usually by skilled workers specially trained to perform the various construction steps. Upon completion, the packaged generator is shipped, usually over railroad lines, to the point of eventual use where it is installed into the steam supply system.

Tl-Ie basic components of a water-tube packaged steam generator are the drums or headers which are partially filled with water, means for supplying heated gas or the like, into a furnace area, and tubes connected between the drums in which water flows. The furnace area is defined by an arrangement of tangential water-tubes which are radiant heated by the gases to have water contained therein converted into steam. An additional bank of tubes is heated by convection to convert water therein into steam. The steam generated in the tubes enters into the water in the upper drum and bubbles through the water into the upper surface, and then into the space above the water level in the upper drum. There the steam collects and passes through an outlet for passage to the location at which the steam is to be used.

There are three basic designs of such boilers presently being manufactured each of which has its own unique points of advantage and corresponding areas of difficulty or inefficiency. In the so called A" type boiler or generator, a single upper drum is connected by two runs of tubing to two lower, generally smaller diameter, drums. The space defined between the tubing sections defines a furnace area in which the heated gases are produced and delivered to heat the water flowing in the tubes. While the A type boiler provides a relatively large heating or furnace area, the requirement of a third drum increases the cost and complexity of the system. The type boiler design, requires only two drums, and has two sections of bent tubing extending between the drums in opposite directions. The furnace area, defined in the space between the tubing is, however, limited and is of necessity less than that obtainable in the A" type unit. The heating or stream generating capacity per unit volume of 0" generators is thus correspondingly limited.

In an attempt to overcome the limitations of the O generators while still utilizing only two drums, the D" type generator was devised. In this generator the upper drum is disposed directly above the lower drum, a first run of tubing extends vertically between the drums, and a second run of bent tubing, usually having a fewer number of tubes than the vertical run, extends outwardly and then downwardly between the drums so that the two runs of tubing define the letter D when viewed in the vertical plane. The lateral extension of the second run of tubing provides the desired increased volume available for the production of heating gases.

The D" generator thus combines the best features of the A" and 0" generators, in that it requires only two drums as in the latter, while providing the larger furnace volume as in the former.

It has, however, been found that the outer longer run of tubing in the conventional D generator tends to burn out and fail at a relatively high rate and at a much higher rate than the shorter tubing. This in turn requires the frequent disabling of the furnace to make replacement and repairs. The necessity for downtime of the generator for the purposes of such repairs is a source of increased cost, lower efficiency of the generator and considerable annoyance, which has resulted in a reluctance by industry to make use of generators of this type.

The cause of failure of the outer run of tubing is believed to be the reduced flow of water in that tubing as compared to the greater flow of fluid through the shorter vertical run of tubing, since the pressure across both runs of tubing is equal. The relatively low flow rate of water in the outer tubing reduces the cooling of that tubing with the result that the metal surface thereof tends to become significantly hotter than that of the shorter vertical tubing. As a result, the outer tubing is frequently caused to overheat and thus to fail.

Since the packaged generator is transported from the factory where it is constructed to its eventual location of use, the generator which is often of considerable size and weight is preferably designed to achieve ease of handling, shipping and rigging. In some packaged generators and particularly those of the D type construction described above, the center of gravity of the unit is markedly off center and thus handling and shipping are frequently troublesome. In a shipment of generators of this type special additional structure, such as cast concrete blocks to balance the load, must often be provided in the railroad car to insure proper handling and stability of the packaged generator during its transit. This requirement adds to the shipping weight of the packaged generator and thus increases the shipping cost, which in turn is reflected as a higher cost to the purchaser.

It is, therefore, an object of the invention to provide a packaged steam generator having increased heating capacity and increased reliability and useful life.

It is a further object of the present invention to provide a packaged steam generator of the two-drum type, in which substantially uniform fluid flow is achieved in the tubing between the drums.

It is another object of the present invention to provide a D type packaged generator in which likelihood of tube burnout or failure due to overheating is significantly reduced.

It is yet a further object of the present invention to provide a packaged generator of the type described in which greater weight balance is achieved, thereby simplifying shipping and handling of the unit.

Briefly described, the packaged steam generator of the present invention is basically of the D" type, having all the advantages of that type of generator without the likelihood of the outer run of tubing being overheated as a result of the nonuniform flow of water through the tubing as in the conventional D type generators. In accord with the present invention, the upper and lower drums are laterally displaced to permit the outer run of tubing to be substantially the same length as the main run of tubing between the drums, thereby to insure substantially uniform fluid'flow in both runs of tubing. This has the desired effect of establishing uniform cooling of both runs of tubing and thereby insures increased reliability of the generator due to the reduced likelihood of tube burnout.

The arrangement of the drums and tubing in this manner permits the design of a D type generator with all the advantages described above, while still establishing a center of gravity located approximately along the vertical center line of the generator which is not possible in the conventional D type generator. The improved weight distribution is desirable in improving the ease and efficiency of shipment and handling of the generator such as in a railroad car, since the load may now be centered on that car without the need for additional balancing counter weights.

To the accomplishment of the above and to such other objects as may hereinafter appear, the present invention relates to a packaged steam generator as defined in the appended claims, and as described in the following specification taken together with the accompanying drawings in which:

FIG. 1 is a side elevation of a packaged steam generator of the present invention;

FIG. 2 is an end elevation of the generator of FIG. 1 as viewed in the direction of the arrows 22 of FIG. 1;

FIG. 3 is a vertical cross-sectional view, in an enlarged scale, taken approximately along the line 33 of FIG. 2;

FIG. 4 is a vertical cross-section taken along the line 4-4 of FIG. 2;

FIG. 5 is a cross-sectional view taken along the line 5-5 of FIG. 3;

FIG. 6 is a cross-sectional view taken along the line 6-6 of FIG. 3; and

FIG. 7 is a vertical cross-section taken along the line of 7-7 of FIG. 3.

In the drawings the packaged steam generator of the present invention is illustrated in the form of a bottom-supported, natural circulation steam generating unit designed to operate with oil, gas or combination firing and available in various standard sizes to produce steam at ranges up to 150,000 lbs. of steam per hour at operating pressures up to 900 lbs. per square inch.

The steam generating unit is housed in an integral substantially rectangular setting having front and rear walls 10 and 12, side walls 14 and 16, and an upper enclosing wall or roof 18. A upper drum 22 extends along wall 18, as shown in FIG. 1, Iongitudinally along the full length of the unit, and a lower drum 24, which may be of a smaller diameter than drum 22, is arranged along the lower section of the unit and also extends along the entire length thereof. As seen best in FIG. 5, a first bank or run of tubes generally designated 26 extends between drums 22 and 24 and radially enters a lower periphery of drum 22 and the upper periphery of drum 24. A second run of tubes 28 also extends between the drums 22 and 24. Tube 28 includes a first horizontal run 30 extending beyond the vertical center line of drum 22 and is there bent at a right angle bend to form a vertical run 32 which radially enters the bottom periphery of the drum 22 along with the upper terminations of tubes 26.

The arrangement of the water tubes 26 and 28, as shown in FIG. 5, extends, as shown in FIG. 3, substantially the entire length of the unit. In addition, tubes 42 and 44 are arranged tangentially along the rear inner wall of the generator, and tubes 26a extend from the bank of tubes 26 to the rear wall of the generator. A central furnace area 34 is defined in the interior of the generator by tubes 28, 42, 44, 26a and the inner .tangential row 26b of tubes 26. A burner 36 extends through front wall 10 into the furnace area. Drum 24 is filled to its capacity with water and drum 22 is also filled with water to approximately half of its capacity. The heated gases escaping from the forward end of burner 36 are forced such as by a blower into area 34 at high temperatures and heat the water in the tangential tubes defining the furnace area 34 and then by convection heating, heats the water flowing in the interior ones of tubes 26. The heated water in the tubes is converted into steam which rises and then passes into drum 22. The steam in drum 22 bubbles up through the water into the open area above the water level, and passes through a steam outlet 38 toward its eventual area of utilization.

As the gases flow through the convection tube bank 26 towards the front of the unit and the flue gas outlet 40, the tubes to the rear of the unit in bank 26 may be defined as risers and the tubes toward the front of the unit in bank 26, which are heated to a lesser extent, serve as down-comers to return water from upper drum 22 to lower drum 24 for subsequent reheating and conversion into steam.

The exhausted heated gases after being cooled by the absorption of their heat by the water in the tubes is passed out from the unit through a single upper output flue 40 arranged at forward end of upper wall 18.

The novel features of the present invention are illustrated in FIG. 5 wherein is shown the layout and arrangement of the upper and lower drums 22 and 24 with respect to the two sections of bent tubes 26 and 28 connected therebetween. The tubes 26 and 28 are arranged in basically the D form to define a relatively large furnace space 34 in which the heated gases are active to heat the water flowing in the tubes. As opposed to a conventional D type boiler wherein the upper and lower drums are arranged along the same vertical center line, drums 22 and 24, in the generator of the present invention; have their vertical center lines displaced. This displacement of the upper and lower drums permits the length of tubes 26 and 28 to be substantially the same, which was heretofore not feasible in D" type boilers in which the single outer run of tube is of necessity significantly longer than the vertical run of tubes between the drums. The equal length of tubes 26 and 28 insures that, as a result of the equal pressure differential between the upper and lower drums, the rate of water flow in tubes 26 and 28 will be substantially uniform, and the resultant rate of cooling of the metal surfaces of the tubes will also be substantially equal. This equal cooling of the tubes serves to prevent the overheating and thus the premature burnout or failure of tube 28 as is desired.

The arrangement of the tubes 26 and 28 extends substantially along the entire length of the generator setting. Tube 28 comprises a single row of tubing lying tangentially along side wall 14, the water flowing through tube 28 serving to cool that side wall. The outermost row of tubes 26 is similarly arranged tangentially along side wall 16 and the water flowing in those tubes is effective to cool wall 16 and maintain its temperature at a sufficiently low level. As can be seen in FIG. 4, the innermost rows of tubes 26 terminate short of the rear of the setting with the tangential outer row 26a extending until the inner surface of rear wall 12.

As shown in FIG. 6, a plurality of tubes divided into two sections of bent tubes 42 and 44 are arranged tangentially along the inner surface of rear wall 12 and extend between drums 22 and 24. The tangential arrangement of tubes 42 and 44 along the inner surface of rear wall 12 serve to cool the rear wall. Both sets of tubes 42 and 44 are radiantly heated to form steam but nevertheless both contribute to the rear wall cooling. The outer rows of tubes 42 and 44 are also tangential to side walls 14 and 16 respectively, to aid in the cooling of those walls.

As shown in FIG. 4, rear wall 12 has an inner layer of refractory tile 46, an intermediate heat insulating layer 48, and an outer sheath or casing 50. An additional section of bent tubes 52 (FIG. 7) extending between and into drums 22 and 24 is arranged in insulating layer 48, and lies tangential to the outer surface of refractory layer 46. The water flowing through these tubes is essentially unheated by the furnace gases and serves to cool layer 46. As shown in FIGS. 5 and 6 additional refractory insulation 49 may be provided at the ends of the tubes which enter radially into drums 22 and 24 to prevent the bypassing of the furnace gases from the furnace area directly into the convection bank 26, and further to protect direct contact between the steel intercasing and the hot gases where the furnace side wall and convection side wall tubes are no longer tangent to one another or where they open up to enter into the drums.

Side walls 12 and 14 each comprise a metallic, pressure containing plate 53, an insulation block layer 54, and an outer casing 56, and front wall 10 comprises an inner refractory layer 58 and an intermediate insulating layer 60 over which an outer casing 62 is formed. The steam generator of the invention is bottom supported by spaced structural steel members 64 which extend transversely of the unit, and by longitudinal beams 66 which extend the length of the setting. The drums 22 and 24 each have a manhole opening 68 to enable the drums to be serviced and cleaned whenever necessary.

The lateral offset spacing of the drums 22 and 24 along with the arrangement of the tubes 26 and 28 in the manner described above, causes the center of gravity of the unit to be located approximately along its vertical center line. This feature, which is not possible in the conventional D type generator, greatly facilitates the handling and shipping of the generator since its load is more evenly distributed.

The features of improved weight balance and the uniform water flow and cooling of the tubes are thus possible for the first time in a D type packaged steam generator as constructed in accord with the present invention. Tl-Ie steam generator of the invention thus provides the increased steam generating capacity and operating efficiency of the conventional D type generator without the difficulties commonly encountered in generators of this type, particularly the rapid burnout of the longer outer tube.

While only a single embodiment of the invention has been herein specifically described, it will be apparent that modifications may be made therein without departing from the spirit and scope of the invention.

1 claim:

1. A water heating unit comprising a housing including side, rear, upper and lower walls, said real wall comprising 'an inner refractory layer and an insulating layer in thermal communication therewith, a first drum and a second drum in said housing, said second drum being disposed beneath and substantially parallel to said first drum and being laterally offset from said first drum, a first run of tubing extending between said first and second drums, a second run of tubing extending between said drums and defining with said first run of tubing a heating space, the length of said first run of tubing being substantially equal to that of said second run of tubing, thereby to establish substantially equal fluid flow in said first and second runs of tubing, a third run of tubing connected between said drums and lying substantially tangential to one surface of said rear wall, and a fourth run of tubing also connected between said drums, disposed in said insulating layer and arranged substantially tangential to said refractory layer.

2. The unit of claim 1, further comprising a heating unit disposed in said space, said housing defining an enclosure for said tubings and a support for said drums, the arrangement of said drums and said tubing being such that the center of gravity of said unit lies substantially along its central vertical axis.

3. The unit of claim 2, in which one of said first and second runs of tubing comprises a single tube arranged substantially tangential to one of said side walls, the other of said runs comprising a plurality of rows of tubing, the outermost one of which lies substantially tangential to the other of said side walls. 

1. A water heating unit comprising a housing including side, rear, upper and lower walls, said real wall comprising an inner refractory layer and an insulating layer in thermal communication therewith, a first drum and a second drum in said housing, said second drum being disposed beneath and substantially parallel to said first drum and being laterally offset from said first drum, a first run of tubing extending between said first and second drums, a second run of tubing extending between said drums and defining with said first run of tubing a heating space, the length of said first run of tubing being substantially equal to that of said second run of tubing, thereby to establish substantially equal fluid flow in said first and second runs of tubing, a third run of tubing connected between said drums and lying substantially tangential to one surface of said rear wall, and a fourth run of tubing also connected between said drums, disposed in said insulating layer and arranged substantially tangential to said refractory layer.
 2. The unit of claim 1, further comprising a heating unit disposed in said space, said housing defining an enclosure for said tubings and a support for said drums, the arrangement of said drums and said tubing being such that the center of gravity of said unit lies substantially along its central vertical axis.
 3. The unit of claim 2, in which one of said first and second runs of tubing comprises a single tube arranged substantially tangential to one of said side walls, tHe other of said runs comprising a plurality of rows of tubing, the outermost one of which lies substantially tangential to the other of said side walls. 